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Making waves: The power of concentration gradients - Sasha Wright

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The constant motion of our oceans represents a vast and complicated system involving many different drivers. Sasha Wright explains the physics behind one of those drivers -- the concentration gradient -- and illustrates how our oceans are continually engaging in a universal struggle for space.

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Meet The Creators

Educator Alexandra (Sasha) Wright

Collaborator Ellen Herra

Director Andrew Foerster

Sound Designer Devin Polaski

Artist Sarah Pedro

Editor Emma Bryce

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Understanding
the physical mechanisms that underlie ocean circulation is essential to
managing the incredible diversity of life that is found exclusively in marine
habitats. Ocean habitats are some of the
most diverse and spacious. Oceans cover
71% of the surface of the globe and comprise 50-80% of
the Earth’s biota. In particular, coral reefs are
biodiversity
hotspots where an
especially large number of species can be found; but these same species are
also particularly threatened due to human activities. When
biodiversity is high it can help buffer against big disturbances (such as climate change
and pollution) in the future. When
biodiversity is driven to low levels, it may also make these systems more
susceptible to collapse.An
understanding of concentration gradients is incredibly important for
understanding most physical phenomena on earth: from ocean circulation, to osmosis/diffusion,
electricity, plant water use, human oxygen consumption, and pest
management. To learn more about the role
of concentration gradients in each of these processes, read below and click the
links.Ocean Circulation: Ocean circulation is driven by
many things (wind, surface currents, thermohaline circulation, tides). But understanding just a small part of this
process is important. Furthermore,
concentration gradients in oceans are based on physical properties that can help
us understand more about the physical world in general. Read more here.Osmosis: No matter how complicated it
sounds in your biology textbook, osmosis is the simplest form of a
concentration gradient. This is the
simple movement of water molecules from a high concentration to a low
concentration. But this is the special
word just for water concentration gradients. Read more here.Diffusion: Similarly, diffusion is the
word we give for the movement of solutes (ions, etc) from high concentrations
to low concentrations (but don’t get confused, on a physical level these
processes are exactly the same!). Read more here.Electricity: one side of a battery is
rich in electrons, and the other side is deficient in electrons. The electrons
want to move from high concentrations to low concentrations but they are separated
by an impenetrable wall. They can only equilibrate when the two sides of the
battery are connected by a wire forming an electronic circuit (or when a switch
is flipped completing the continuity of that wire). Read more here.Water loss in plants: Plants need H2O for
basic metabolic functions (photosynthesis), but they also lose water as a
byproduct of photosynthesis. The leaf of
a plant has tiny little pores (similar to the pores on your face) that the
plant can open or close depending on the conditions of the day. A plant has to open these pores in order to
conduct photosynthesis (and let CO2 in), but in the process H2O escapes. This is due to concentration gradients. The air surrounding a plant almost always has
less water in it than the intracellular space inside the plant’s leaf. This creates a concentration gradient from
high concentration inside the leaf to low concentration outside the leaf. When the plant opens the pores on the
surface, water molecules randomly bounce out of the leaf surface and into the
air. Read more here.Human lungs and oxygen: Similarly to water diffusing
out of the plant, O2 is in high concentrations in the air we breathe. Conversely, O2 is in low concentrations in our
blood as it enters into the area surrounding our lungs. O2 diffuses into the lungs in the alveolar
air space for as long as the concentration in the air spaces around the blood
is higher than the blood itself. Read
more here.Pest
management:
hHve you ever had a friend with a garden who uses salt to control pesky
slugs? The reason it works is because of
concentration gradients. When you pour
salt on the surface of the slug, the relative amount of water on the slug skin
is lowered (because now some of that space is taken up by salt). This establishes a concentration gradient
from the inside of the slug (high water) to the outside of the slug (relatively
low water) that allows all of the water inside the slug to randomly bounce
out. This eventually dehydrates the slug
and kills it.

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TED-Ed Original lessons feature the words and ideas of educators brought to life by professional animators. Are you an educator or animator interested in creating a TED-Ed original? Nominate yourself here »